English rock-bristle  (Seligeria calycina)

Classified as Lower Risk in Great Britain and Vulnerable in the provisional Bryophyte Red List for Ireland (4).

English rock-bristle is a small moss with narrow leaves, which grows in patches on shaded chalk (2).

This species is endemic to Europe; in Britain it has a wide distribution in the chalklands of southeast England, reaching up to Humberside and down to south Devon (4). Outside of Britain it is very rare; it has been recorded from Belgium, France and Italy (4).

Inhabits various sizes of chalk fragments, typically found on the ground in woodlands, but it also occurs in chalk pits and, very rarely, chalk grassland (5).

Little is known of the biology of this species. Mosses, hornworts and liverworts form a group of plants called bryophytes (6). Bryophytes lack many of the more complex structures of the higher plants, such as a vascular system, and flowers. They do not have roots, instead they have structures called 'rhizoids' which absorb water and anchor the plant to the substrate. All bryophytes have an interesting life-cycle consisting of two main parts, called the gametophyte and sporophyte generations (7). Plants that are in the gametophyte stage can reproduce sexually. Male organs (antheridia) produce male sex cells or gametes called antherozoids, which actually move to the female sex organs (archegonia) (7) through water droplets (8). Fertilisation occurs and a plant develops called a 'sporophyte', which remains attached to the plant. The sporophyte releases spores from within a capsule; the spores disperse and develop into a new gametophyte-stage plant (7).

Habitat loss resulting from development, road building and conversion to arable farming, as well as scrub growth (resulting in excessive shading) and unsuitable management or loss of woodlands are all thought to pose threats to this species (4).

A Species Action Plan has been produced for this moss under the UK Biodiversity Action Plan. This plan aims to maintain the current range of the species. Several populations occur within Sites of Special Scientific Interest (SSSI), and therefore receive a degree of protection (4).

Information authenticated by Royal Botanic Gardens, Kew:
http://www.rbgkew.org.uk/

• Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
• Gametophyte: a life cycle stage in plants, which has one set of chromosomes (threads of DNA protein) in the cell nucleus (a condition known as ‘haploid’), which arises from a spore (which is also haploid). Sex cells (gametes) are produced during the gametophyte stage. This is the dominant life-cycle stage in liverworts and mosses.
• Rhizoids: thread-like structures that help to anchor the plant to the substrate, and absorb minerals and water. In liverworts they consist of a single cell, in mosses they are multi-cellular.
• Spore: microscopic particles involved in both dispersal and reproduction. They comprise a single or group of unspecialised cells and do not contain an embryo, as do seeds.
• Sporophyte: the stage of a plant life cycle that produces spores (microscopic particles used in dispersal and reproduction). This stage is diploid (in the cell nucleus there are two sets of chromosomes - threads of DNA protein) and is dominant in ‘higher’ plants such as flowering plants.
• Vascular system: in plants, the system that allows water and nutrients to move around.

1. National Biodiversity Network Species Dictionary (August 2002) http://www.nhm.ac.uk/nbn/
2. Smith, A. J. E. (1978) The moss flora of Britain and Ireland. Cambridge University Press, Cambridge.
3. Watson, E. V. (1995) British mosses and liverworts, 3rd edition. Cambridge University Press
4. UKBAP (August 2002): http://www.ukbap.org.uk
5. Hill, M. O., Preston, C. D, & Smith, A. J. E. (1992) Atlas of the Bryophytes of Britain and Ireland. Volume 2. Mosses (except diplolepideae). Harley Books, London.
6. Church, J. M., Hodgetts, N. G., Preston, C. D. & Stewart, N. F. (2001) British Red Data Books: mosses and liverworts. Joint Nature Conservancy Committee, Peterborough.
7. Mosses and Liverworts in Wales (August 2002): http://home.clara.net/adhale/bryos/
8. Egerton, H. & Jones, F. (Eds.) (1998) Nature Encyclopedia. Dorling Kindersley, London.